Gas-engine.



No. 865,267 PATENTED SEPT. 3, 1907'. H. POLLARD.

GAS ENGINE.

APPLICATION FILED JULYZ. 1907.

SSHEETS-SHEBT 1.

. waldo!" N0.,865,267- PATENTED SEPT. 8, 1907.

H. POLLARD. GAS ENGINE.

. APPLICATION FILED JULY2,1907.

a SHEETS-EHIEET 2.

ill/ l No. 865,267. PATENTED SEPT. 3, 190?.

- H; POLLARD. GAS ENGINE.

APPLIOATION FILED JULY2,1907.,

3 SHEETS-SHEET 3.

HENRY PQLLARD, OF PAISLEY, SCOTLAND.

GAS-ENGIIIE.

Specification of Letters Patent.

Patented Sept; 3, 1907.

Application filed July 2, 1907. Serial No. 881,869.

To all whom it may concern: Q 0

Be it known that I, HENRY Pentium, 9. subject of the King of Great Britain, residing at Paisley, Scotland, have invented new and useful Improvements in Gas- Engines, of which the following is a specification.

My invention comprises a gas engine having a variable throw to its crank, imparting to its piston variable strokes and velocities, so as to get a greater range of; expansion by drawing in the charge and compressing it with a short stroke and then expanding and exhausting 'with the'larger stroke. Of the total amount of heat obtained from the products of combustion in a gas engine cylinder, only 25 7g, is converted into useful work; 40 70 is absorbed by tbewater jacket, and thercniaining 35 is lost in the exhaust gases due to incomplete expansion. With the present cycle of operations where the working piston does work as the pump as well, the expansion volume is limited to that of the volume before compression, as with. the ordinary crank the strokes must obviously be of equal length.

idea is to employ a crank capable of giving vari able strokes and consequently variable velocities to the piston, and thus giving a greater range of expansion than at present exists, which will considerably increase the efficiency of the engine.

The invention. is shown in the accompanying drawing in which,

Figure lv is a part elevation and part sectional view of the invention. Fig. 2 is a transverse vertical sectional view through the frame, crank pin and adjacent parts, on the line 2 2 of Fig. 1. Figs. 3 and 4 are detail views relating to the crank pin and crank arm. Fig. 5 is a side elevation of a modified form of apparatus adapted for vertical engines. Fig. 6 is a side view of another modification. Fig. 7 is a plan view of the parts shown in Fig. 6. i

The crank 1 is of a-built up type, that is, its crank pin 2 is not made integrally with the arms, but slides in. ways 3 up the face of each arm, and thus its position from the center of the shaft can be varied to give differ-- ent lengths of travel to the connecting rod attached to it. Its position .irom the center of rotation is governed by two series of grooves 1, 5 in stationary brackets 6 fixed immediately beside the two crank arms; with which grooves a grooved switch block 7 cooperates to shift the crank pin from one groove or series of grooves to the other. longitudinally at 8, 2 and 4 and the crankpin projects through'these slots and candes'at each end a roller 9, each of which. is adapted to travel in the grooves of the bracket above mentioned.

,The outer groove 5 of each pair or series is made con centric to the crank shaft, and the inner groove 4 cc centric to it. As the crank shaft rotates with the rollers movin in the outer grooves, the crank pin is kept in The crank arms are slotted centrally and the one position at the outer end of the sliding ways in the crank arms and gives a long stroke to the piston. If, however, the rollers on the ends of the crank. pin had been in the inner grooves which are eccentric to the crank shaft, the crank pin would have been drawn arms revolve and would have given a short stroke to the piston.

For the first "we strokes of the piston the crank pin follows the inner grooves making short strokes, writer the next two strokes the crank pin is changed into the outer grooves making long strokes. The changing or switching from one series of grooves to the other is accomplished by means of the vertical sliding block or switch, Starting from a position a, Fig. 1, 1n the outer groove the crank pin keeps at the end of the arms in 60 down the sliding ways of the crank arms as the said traveling from x to y, a distance equal to the expansion stroke, in the meantime the sliding switch block 7 has been brought down to its lower position to locate its groove as ihdicatedin dotted lines, Fig. 1, and the crank pin travels back from y to its first position x, i. e. a distance equal to the exhaust stroke... Starting out again, the crank pin this time, due'tolths altered position of the sliding switch block, traverses the inner groove from x to z and is thus drawn down in the'arms and making a short stroke equalto the suction stroke.

In the meantime the sliding switch block has been moved back to its former position again and the crank pin travels back from 2 to its original position at x-during which the crank pin is moved up to its former position again at the end of the arms (equal tothe compression stroke), when after ignition the crank pin starts out again in the outer groove. The lifting and lowering of the sliding or switching blocks 7 (of which there are two, one for each side of the crank pin), and

holding them in position while the crank pin is switched from one groove to the other is accomplished by means of two came 10 rigidly keyed to a shaft 11, this shaft making one half revolution for each revolution of the crank shaft, or the same'speed as the lay shaft from which it is driven by spiral or other gears 12. The cam should, however, be made double to insure a positive switching action. g

As shown in Fig/ 5 the invention may be applied to a.

vertical engine suitable for automobile engines; in this 100 haust valve is formed on the periphery of the other 105 cam. The stationary brackets having the grooves cut in their faces iorfcontrolling the position of crank pin can also be made to do double service as columns to n the cylinder.

As shown in Figs. 6 and 7 I may employ a modifica- 11b tion of the switching arrangement; the switching block 7 X in this case takes a circular form and is altered from i one position to the other by means of a rod 14 connected to a cam as in the last case, and moves the circular switching block through the medium of the lever 15 and shaft 16 which shalt is formed integrally with the circular switch block I prefer the sliding switch block as it is susceptible of adjustment. The crank pin can be adjusted for wearin sliding up its ways in the'arms by screwing down two gibs 17, Fl". 4.

This arrangement will considerably increase the efficiency of the engine not only by means of the greater range of expansion procurable, but by the following two valuable featuresz-There is a difference in velocities of the piston between short and long strokes for the short strokestakes place in the same time that the long one does, and is therefore slower so that ll the suction stroke takes place slowly, insuring that the gases are at atmospheric pressure before compression commences, giving a higher compression, which means a much higher efiiciency, and (2) the" expansion stroke is quicker than the suction one, as it has 50% more distance to travel in the same time, hence the heated gases alter ignition expand more quickly, more of the heat being-converted into useful work in driving out the piston, and less radiating into the water jacket and cylinder walls.

The two grooves, or especially theinner eccentric grooves, need not be true circles, but may be curves of any desired shape to vary the stroke of the crank to suit its application, which may be applicable to purposes other than for gas engines.

The groove in the sir-itch, block must be a curve in order to suit itself to the two different diameters of the grooves.

it will be observed-that my invention consists of cam grooves for controlling thetravelof the crank pin to give the piston long andshort strokes and the said crank pin being shifted from one cam groove to the other by a switch block operating automatically and having a groove therein which is common to the two grooves above mentioned in that it forms the connection between them or the complement thereof.

Having now particularly described and ascertained the nature of my said invention and in What manner the same to be performed, I declare that what I claim is: I

1. ln n gas 1' zine, the means for giving to the piston a long and a Sllfiit stroke consisting of the grooves in the trame tor rec vivlng an extension of the crank pin which is arranged to shift along the crank arm, substantially as ihed.

2 in ages loin: and a short stroke, consisting of the grooves for receiving an extension of the crank pin and the switch piece having; the complement of said grooves with means for shifting said switch piece, the said crank pin being movable along the crank arm, substantially as described.

3. in combination with the crank arm and crank pin of :1 gas i-ngine, :i grooved member and a grooved reciprocating- S \'iicllill0('l( cooperating therewith and receiving; a pill! of the crank pin to control the stroke, said crank pin being movable along the crank arm, substantially as do Sl'l'li in festilliuny wher of I have signed my name to this specification in the presence of two subscribing witnesses.

engine. the means for giving the piston 11- 

